Device and method for spraying a combustible liquid

ABSTRACT

The invention relates to devices and methods for the assisted internal spraying of a combustible liquid, wherein the combustible liquid is fed into a combustion area through a passage which ends in an outlet opening and into which spray gas is fed via a plurality of channels, the passage including a narrow portion and a wider but relatively short pre-spray chamber downstream from the narrow portion, the channels including small-diameter end sections tangentially leading into the narrow portion of the passage near the input opening of the chamber such that the spray gas impacts the combustible liquid and imparts a helical movement to the combustible liquid.

The present invention relates to devices and methods for the internal assisted atomization of a combustible liquid.

Effective combustion of a liquid in a hearth requires the liquid to be atomized into fine droplets which evaporate under the effect of the heat within the hearth. The evaporated liquid then burns with an oxidant inside the hearth.

In the case of assisted atomization, atomization is performed by a jet of the liquid being torn apart by a high-velocity flow of gas to form an atomized jet (or spray) of droplets of the liquid which are dispersed in the gaseous phase.

The atomization step is of key importance because the properties of the flame obtained at the outlet of the atomization device are very much dependent on the quality and properties of the atomized jet formed, such as the mean droplet size, the droplet size distribution, the penetration length of the atomized jet, the angle of the atomized jet, and the velocity at which it is ejected.

Thus, for example, emissions of unburnt particles are greatly dependent on droplet size.

Unburnt substances may be contained in soot formed by the incomplete combustion of light fractions of the combustible liquid in a zone that is locally hot and oxygen lean. Unburnt substances may also be present in the form of hollow carbon-containing solid particles of large diameters, referred to as cenospheres, which are the result of the incomplete combustion of the largest droplets.

In what follows, the terms “light” and “heavy” are used with reference to the combustible liquid in the sense of light fuels and heavy fuels according to terminology that is commonplace in the field of combustion.

The unburnt substances, once they have left the hot zones of the flame, limit the energy efficiency of the hearth and constitute a significant proportion of the pollutants emitted by the plant and the nature and quantity of which are increasingly strictly limited by regulations.

Unless special precautions are taken, the problem of unburnt substances is heightened in the case of oxycombustion where the flame volume is normally smaller.

In addition, in cool-wall hearths, such as steam-generating boilers, there is a risk that the large droplets will not burn sufficiently quickly to be completely consumed before they reach the cool walls, such as the steam tubes. The liquid, upon contact with the cool walls, gives rise to carbon-containing residues on these cool walls through a quenching effect. This has the effect of reducing efficiency and causing premature damage to the installation. The heavier the fuel, the cooler the walls and the more closely confined the hearth, the more carbon-containing residues will be formed on the cool walls.

In order to achieve the completest possible combustion, to reduce the formation of unburnt substances such as soot and cenospheres, and limit the degradation of hearths with cool walls, it is necessary to limit the size of the largest droplets and the mean size of the droplets generated by the atomization means.

Unless special precautions are taken, in the case of oxycombustion, the amount of heat released by the root of the flame is extremely high with temperatures that may reach levels of the order of 3000° C. This may lead to overheating of the burners and notably of the atomization devices, the consequence of this being coking of the liquid fuel, which could cause blockages and impair the performance and mechanical integrity of the burners and atomization devices and of the hearth if the flame is deflected or extinguished.

A distinction is made between internal assisted atomization and external assisted atomization.

External assisted atomizers of the coaxial type for liquid fuel, such as those described in the literature (Technique de l'ingénieur—“équipment de combustion pour combustible liquide et gazeux [Combustion equipment for liquid and gaseous fuel]”, “Atomization & Sprays”—A. H Lefebvre), are robust systems that also enjoy high atomization quality. These injectors produce very fine atomized jets thanks to the use of a large amount of high velocity atomization gas. Typically, the ratios of mass flow rates of atomization gas to liquid fuel (A/F) involved are of the order of 20 to 40% and even up to 70% in the case described in EP-A-0687858. The large amount of atomization gas flowing around the injection of the liquid fuel also provides thermal insulation and buffer limiting the rise in temperature of the liquid fuel and limiting the extent to which it becomes coked onto or inside the atomizer. The counterpart of this is the impaired energy efficiency caused by the introduction of a significant quantity of generally completely or predominantly inert (in terms of combustion) gas into the hearth via the atomization gas. For example, in the case of a boiler, it is known practice to use a significant proportion of the steam produced for atomizing the liquid fuel, this leading to a reduction in the overall efficiency.

High-performance internal assisted atomization systems are described in FR-A-9509199 and FR-A-9907030. These consist of a stack of several successive inserts:

-   -   primary and secondary nozzle in the case of FR-A-9509199     -   atomizer, spray nozzle and sleeve in the case of FR-A-9907030.

These technologies employ atomization of the liquid which is assisted by a pressurized gas within the atomization device and produce atomized spray jets made up of very fine droplets. The main disadvantage with these internal assisted atomization technologies lies in the fact that they are highly sensitive to blockage by coking of the liquid fuel and the resulting deteriorations, notably in the case of oxycombustion. Specifically, when the insert stacking system is subjected to a high heat flux generated by the flame derived from the atomized jet, the constituent components of the atomizer expand differently and no longer seal metal to metal. The leaks of liquid fuel thus generated toward the atomization gas circuit and toward the outside of the atomization system will progressively degrade the effectiveness of the atomization and the performance of the burner (by increasing pollutant emissions, lowering the energy efficiency) until the entire atomization spray system has become degraded by coking of the liquid fuel under the action of the heat of the flame. These phenomena are, as a general rule, all the more keenly felt when the combustion is enriched with oxygen, because of the higher flame temperature.

Internal assisted atomization devices of type Y are generally made up of a single insert. They are thus more robust to heat flux. Widely described in the literature (Technique de l'ingénieur—“équipment de combustion pour combustible liquide et gazeux [Combustion equipment for liquid and gaseous fuel]”, “Atomization & Sprays”—A. H Lefebvre) or in EP-A-0676244, their key disadvantage is still their limited performance. Specifically, these injectors produce atomized jets or sprays characterized by a higher mean droplet size and a larger proportion of large droplets, which will be responsible for the formation of unburnt substances and for limiting the energy efficiency. The design of these atomizers is based on an annular canal guiding the liquid fuel along the atomization gas central canal in order to create fine droplets. The thermal resistance of these concepts is relatively limited, notably in the case of combustion in oxygen, because inside the atomizer before being mixed with the atomization gas, the liquid fuel is subjected to the heat flux of the flame with no thermal protection from the atomization gas circuit as is the case with external assisted atomizers.

One specific internal assisted atomizer is described in EP-A-263250. This atomizer for a post-mixing burner comprises: (1) a liquid fuel passage having a first portion of relatively small cross section, a second portion of increasing cone-shaped cross section, and a third portion of relatively large cross section, this third portion communicating with a furnace zone and (2) three to seven gaseous atomizing fluid passages, said passages having an injection end in communication at an angle of 45° to 75° with the fuel passage. The atomizer fluid passages terminate near the entry to the cone-shaped second portion so as to direct the atomizing fluid into this second portion near the start of the cone. This atomizer may be made up of a one-piece component. A “one-piece component” means a component that is formed as one piece as opposed to a component that has been assembled.

The atomizer according to EP-A-0263250 thus makes it possible to avoid the problems associated with the atomizers that comprise several inserts. The performance of the atomizer according to EP-A-263250 does still remain limited with, as is the case with type Y atomizers, atomized spray jets characterized by relatively large mean droplet sizes and a large number of large droplets.

It is an object of the present invention to allow a combustible liquid to be atomized by assisted internal atomization with a reduced amount of atomization gas, obtaining a good-quality atomized jet spray, which means to say: (a) one in which the droplets have a mean size (often expressed as a “Sauter mean diameter” or “SMD”) that is sufficiently low and (b) one that contains a low percentage of large droplets.

The present invention notably relates to an injector for injecting an atomized jet of a combustible liquid. The atomized jet is more particularly injected into a combustion zone through an outlet opening of the injector, the combustion zone being situated downstream of this outlet opening. The injector comprises an internal assisted atomization unit.

The atomization unit comprises a downstream injection face which comprises the outlet opening.

The unit also comprises a combustible-liquid passage with an open downstream end and two to six atomization gas ducts.

The combustible-liquid passage passes through the unit and ends at the outlet opening. The passage comprises a narrow part and a preatomization chamber. The passage has a longitudinal axis of symmetry and a substantially circular, preferably circular, variable cross section.

A substantially circular variable cross section is a substantially circular cross section of variable diameter. The longitudinal axis of the passage defines a direction Df of flow of the combustible liquid. A circular or substantially circular cross section notably differs from an annular cross section in that, in the case of a circular or substantially circular cross section, the entire surface area of the circle defined by the cross section is available for the flow of a fluid through the passage in the direction Df.

The narrow part of the passage has a diameter φf.

The preatomization chamber is in the continuation and downstream of the narrow part. It is of a diameter greater than the diameter φf the narrow part. This preatomization chamber has an inlet opening. It ends in the outlet opening of the injector which is situated opposite the inlet opening of the chamber. The chamber has a length Lc in the direction Df between its inlet opening and the outlet opening, and a mean diameter φc.

The narrow part of the passage opens into the preatomization chamber via the inlet opening. The passage ends at its downstream end in the outlet opening of the injector. As indicated hereinabove, said outlet opening of the injector is also the outlet opening of the preatomization chamber.

The length Lc of the preatomization chamber is less than or equal to the mean diameter φc of this chamber.

The atomization gas ducts comprise terminal sections of diameter φg, with φg<φf. Each terminal section opens into the narrow part of the passage near the inlet opening of the chamber. Each terminal section defines a direction Dg of flow of the atomization gas. The terminal sections open into the narrow part in such a way that the directions Dg of flow of the atomization gas form angles Ωgf of between 30° and 90° with the direction Df of flow of the combustible liquid. In addition, the terminal sections open into the narrow part at a tangent to the narrow part. In this way, the atomization gas impinges on the combustible liquid and imparts a helical movement to said combustible liquid.

It should be noted that, when a duct opens into another duct “at a tangent”, the median axes of the two ducts do not intersect. Thus, in this particular instance and in order to impart a helical movement to the combustible liquid, the terminal sections of the atomization gas ducts are oriented with respect to the narrow part of the combustible liquid passage in such a way that the median axes of the terminal sections do not intersect the median axis of the narrow part.

The mean diameter φc of the chamber corresponds to the mean value of the diameter of the chamber along the entire length Lc of the chamber. Thus, when the preatomization chamber is entirely cylindrical, the mean diameter φc of the chamber corresponds to the diameter of the cylinder. When the preatomization chamber is a truncated cone widening between the inlet opening and the outlet opening, the mean diameter φc of the chamber will be the mean of the diameter of the inlet opening and of the diameter of the outlet opening. It should be noted that when the diameter of the preatomization chamber is not constant it is preferable for the diameter to increase toward the outlet opening so as to prevent any coalescence of liquid droplets.

It is known practice to cover the outlet opening of the main passage of an injection device with a cap, with a cover or with a bonnet that is perforated and to inject the liquid into the combustion zone through one or more perforations of said cap, of said cover or of said bonnet. Such injection devices are described in, for example, EP-A-0248539, U.S. Pat. No. 4,708,293, DE-A-19904395 and EP-A-0117472.

The passage of the injector according to the invention on the other hand is a passage with an open downstream end, the outlet opening of which is therefore not provided with such a cap, with such a cover or with such a bonnet.

The atomization unit advantageously comprises three to five atomization gas ducts. A unit with three atomization gas ducts is preferred, because it is effective and simple to produce.

The atomization unit is preferably a one-piece unit, which makes it easier to ensure that the atomization unit is fluid tight.

Advantageously, the length Lc of the chamber is of the order of 0.2 to 1 times the mean diameter φc of the chamber, i.e.: 0.2×φc<Lc≦φc, preferably 0.2×φc<Lc≦0.5×φc. When the length of the chamber is too great, the probability of coalescence increases and an increasing number of large droplets in the atomized jet spray and an increase in the SMD are observed.

The preatomization chamber advantageously comprises at least one substantially cylindrical portion. According to a preferred embodiment, the chamber is entirely substantially cylindrical.

In this context, the chamber or a portion of the chamber is considered to be substantially cylindrical when the walls of the chamber/portion make an angle αc with the direction Df of flow of the liquid fuel that ranges from 0° to 7° (in the direction of said flow).

The substantially cylindrical portion may notably constitute the downstream section of the chamber. When such is the case, the substantially cylindrical portion terminates directly in the outlet opening. It is also possible for the substantially cylindrical portion to open into a frustoconical portion widening toward the outlet opening, i.e. a frustoconical portion the walls of which make an angle of more than 7° with the direction Df of flow of the combustible liquid (in the direction of said flow).

The preatomization chamber may also comprise a frustoconical transient portion (widening toward the outlet opening) connecting the inlet opening of the chamber to the substantially cylindrical portion, the transient portion thus forming the transition between the narrow part of the combustible liquid passage and the substantially cylindrical portion of the chamber. The transient portion advantageously has a length Ltr<¼×Lc, preferably <⅛×Lc and more preferably still < 1/10×Lc. Preferably, the transient portion has a fairly large cone angle θtr, for example greater than 60° and less than 90° (in the direction of flow of the combustible liquid).

According to one advantageous embodiment of the invention, the directions Dg of flow of the atomization gas form angles Ωgf of between 35° and 85° with the direction Df of flow of the combustible fluid, preferably of between 40° and 80°.

For better injector atomization effectiveness, the ratio between the diameter φc of the preatomization chamber and the diameter φf the narrow part of the combustible liquid passage upstream of the chamber is preferably less than 3, namely 1<φc/φf<3, preferably 1.1<φc/φf<2.

The ratio between the diameter φg of the terminal sections of the atomization gas ducts and the diameter φf the narrow part of the combustible liquid passage into which the atomization gas ducts open is beneficially between 0.1 and 1, namely: 0.1<φg/φf<1.0; and preferably between 0.2 and 0.8, namely 0.2<φg/φf<0.8.

The present invention also relates to a burner for burning a combustible liquid, comprising an injector according to any one of the embodiments described hereinabove. The burner is not limited to any one particular type. Thus, the burner may notably be a burner for staged combustion or for non-staged combustion. It may comprise a refractory surrounding the injector according to the invention.

The invention also relates to a furnace for burning a combustible liquid comprising a hearth equipped with at least one injector and/or with at least one burner according to any one of the embodiments described hereinabove. This furnace comprises a combustion zone downstream of the outlet opening of said injector.

The invention is advantageous for a wide range of furnaces, such as the following furnaces: furnaces that burn liquid waste, steam-generating boilers, smelting furnaces, heating furnaces, clinkerization furnaces, precalcination plants, coking furnaces, etc.

However, the invention is of especial benefit in furnaces intended for burning liquid waste, which is often difficult to burn and in respect of which the environmental legislation is often very strict.

Another application in which the invention is of particular benefit is in furnaces the hearth (combustion zone) of which is of relatively small size in the region of the flames, such as short and/or narrow furnaces.

Thus the invention is of notable benefit for cool-wall furnaces. One example of furnaces with cool walls is boilers. In a boiler, the heat energy generated by combustion is used to heat a heat-transfer fluid, typically water or steam, which flows through one or more ducts. The heat energy is transferred to the heat-transfer fluid through the wall or walls of the duct or ducts. Because said walls are in direct contact with the heat-transfer fluid that is to be heated, their temperature remains markedly lower than the temperature obtaining in the combustion zone. Similar cool-wall furnaces are used for the heat treatment of liquids or gaseous phases, such as for “cracking” or “reforming” petrochemical products.

The present invention also relates to a method for the assisted internal atomization of a combustible liquid using an injector according to any one of the embodiments described hereinabove.

According to the method according to the invention:

-   -   a. the combustible liquid passage is supplied with combustible         liquid, and     -   b. the atomization gas ducts are supplied with pressurized         atomization gas,         this being in such a way that the combustible liquid has a flow         velocity Vf in the narrow part of the passage, and such a way         that the atomization gas has a flow velocity Vg in the terminal         sections of the ducts, with Vg>Vf.

The atomized combustible liquid thus obtained is injected into a combustion zone through the outlet opening of the injector.

As indicated hereinabove, the atomization gas impinges on the combustible liquid and imparts a helical movement to the combustible liquid.

It has been found that, notably by virtue of this helical movement of the combustible liquid, it is possible, with the same ratio of atomization gas to combustible liquid, to create an atomized jet spray made up of droplets of lower mean size and containing a lower percentage of large droplets or alternatively to produce an atomized jet spray made of droplets with the same mean size and containing a similar percentage of large droplets but using a lower ratio of atomization gas to combustible liquid.

According to one embodiment, the terminal sections of the atomization gas ducts open into the narrow part of the combustible liquid passage upstream of the preatomization chamber so that the atomization gas imparts a helical movement to the combustible liquid inside the narrow part of the passage.

Preferably, the ducts are supplied with pressurized atomization gas in such a way that the flow velocity Vg of the atomization gas in the terminal sections of the ducts is greater than 80 m/s and preferably less than 600 m/s. Thus, the flow velocity Vg of the atomization gas in the terminal sections may form between 80 m/s and the speed of sound or, when the terminal sections comprise nozzles suited to supersonic injection, between the speed of the sound and 600 m/s.

Advantageously, the passage is supplied with combustible liquid and the ducts are supplied with pressurized atomization gas so as to obtain an atomized jet spray of combustible liquid in the atomization gas leaving the preatomization chamber with an ejection velocity comprised between 1 and 400 m/s, preferably between 100 and 350 m/s. In this context, the ejection velocity will be considered to correspond to the ratio between the volumetric flow rate of the atomization gas and the mean cross section of the preatomization chamber. Thus, in instances in which the preatomization chamber has axial symmetry, which it most often does, the ejection velocity corresponds to the ratio between the volumetric flow rate of the atomization gas and (π×φc²)/4.

The ducts are preferably supplied with the pressurized atomization gas in such a way that the atomization gas is at a pressure of between 1 and 10 bar in the terminal sections of said ducts.

The atomization gas may notably be chosen from steam, air, oxygen-enriched air, oxygen, recycled flue gases and CO₂.

The combustible liquid may be a liquid waste. The combustible liquid may also be a liquid fuel or a solid fuel in liquid suspension (often referred to by the term “slurry”).

When the combustible liquid is a liquid fuel, it may notably be chosen from light fuel oil, heavy fuel oil and petroleum residue. The quality of the atomized jet sprays that can be obtained by virtue of the invention makes the invention particularly useful in the internal assisted atomization of heavy fuel oil. In that case, the atomization gas is advantageously steam. It should be noted that liquid fuels are highly prized in industry for their relatively low cost in relation to gaseous fuels that are easier to burn.

When the combustible liquid is a solid fuel in liquid suspension, the solid fuel is advantageously powdered coal. The suspension may in particular be an aqueous suspension.

The invention also relates to a method for burning a combustible liquid in a hearth, in which the combustible liquid is: (a) atomized and injected into a combustion zone using an internal assisted atomization method according to any one of the embodiments described hereinabove and (b) burnt with an oxidant in this combustion zone. Said combustion zone is typically situated inside a hearth.

The oxidant may in particular be air, oxygen-enriched air or oxygen. Because of the specific properties of oxycombustion, as were mentioned hereinabove, the invention is particularly advantageous when the oxidant is oxygen or enriched air with an oxygen content of at least 80 vol % and up to 100 vol %. The oxidant may also advantageously be a gas containing between 21 vol % and 100 vol % of oxygen and between 20 vol % and 0 vol % of nitrogen, for example: a mixture of oxygen and CO₂ or a mixture of oxygen with recycled flue gases.

When the atomization gas is an oxidant, this atomization gas may constitute at least part of the oxidant used for burning the combustible liquid.

The present invention and the advantages thereof will be better understood in the light of the example hereinafter with reference given to FIGS. 1 to 4 in which:

FIG. 1 is a partial, perspective and transparent schematic depiction of an atomization unit of an injector according to the invention with a cylindrical preatomization chamber and three atomization gas ducts, and

FIGS. 2 a, 2 b and 2 c are partial schematic depictions in cross section of an atomization unit of an injector according to the invention with a cylindrical preatomization chamber and three atomization gas ducts, FIG. 2 c being a cross section at the preatomization chamber, FIG. 2 a being a longitudinal section on A-A through the axis of one of said ducts and FIG. 2 b being a longitudinal section on B-B through the axis of the passage, and

FIGS. 3 a, 3 b and 3 c are schematic depictions similar to FIGS. 2 a, 2 b and 2 c but showing an atomization unit with a preatomization chamber the main part of which is a frustoconical first portion and which also comprises a frustoconical second portion downstream of the first, and

FIG. 4 is a schematic depiction in cross section of the intersection between the narrow part of the combustible liquid passage and the terminal sections of the atomization gas ducts and in which the three atomization gas ducts extend in a plane perpendicular to the narrow section of the passage (Ωgf=90°).

The atomization unit 1 of the injector comprises (i) a combustible liquid passage 30 comprising a narrow portion 31 of diameter φf, (ii) three ducts 20 for pressurized atomization gas, having terminal cross sections 21 of diameters φg tangential to said narrow portion 31 of the liquid fuel passage 30 and of a mixing chamber for mixing the two phases, referred to as the preatomization chamber 10, with a mean diameter φc and length Lc.

The diameter of the chamber 10 is greater than that of the narrow part 31 of the combustible liquid passage 30, the latter diameter being itself greater than the diameter of the terminal sections 21 of the atomization gas ducts 20.

The length Lc of the preatomization chamber is short: less than or equal to the mean diameter φc thereof. This feature avoids the atomization being impaired by the confinement and coalescence of the ligamentary structures and limits the temperature rise of the mixture of atomization gas and combustible liquid, thus making it possible to avoid the combustible liquid coking and blocking the injector.

In the preatomization chamber 10, the liquid fuel is atomized into fine ligamentary structures and fine droplets under the effect of the pressurized atomization gas injected at high velocity via the terminal sections 21 of the ducts 20. Because said terminal sections 21 are tangential to the flow of the fuel in the narrow part 31 of the passage 30, injecting the atomization gas imparts a helical movement (indicated schematically by the arrows 40 in FIG. 4) to the atomization gas/liquid fuel mixture. That encourages the atomization of the liquid.

The liquid is thus atomized by a number of phenomena:

-   -   the high velocity of the atomization gas creates high shear         rates,     -   the tangential injections of the atomization gas create shear         forces in all three dimensions, and     -   because the atomization gas is injected under high pressure         (typically in excess of 2 or 3 bar), its expansion is         accompanied by a shock wave in the preatomization chamber 10 and         this further encourages the breaking up of the liquid into fine         structures.

The fuel injected at low velocity is atomized into fine droplets and fine ligamentary structures as it enters the preatomization chamber 10 through the three tangential injections of pressurized atomization gas. This is notably rendered possible by the high three-dimensional shear rates created with the high gas injection velocities (>80 m/s for a pressure in excess of 2 bar) and by the helical flow of the gas/liquid mixture.

The chamber 10 is characterized by a length Lc less than or equal to the diameter φc thereof (Lc≦φc) thus preventing droplets and ligaments from coalescencing into larger sized structures and preventing the liquid fuel from increasing in temperature. The length Lc of the chamber 10 corresponds to the distance, measured in the direction Df, between the inlet opening of the chamber 10 and the outlet opening 50 of the injector.

The mean diameter φc of the chamber is defined such that the ejection velocity of the dispersed liquid/gas mixture in the combustion zone 100 downstream of the outlet opening 50 is comprised between 1 and 400 m/s, preferably between 100 and 350 m/s. The angle of attack Ωgf of the injections of atomization air at a tangent to the flow of liquid fuel may vary from 30° to 90° according to the desired length of the penetration. Specifically, the higher the angle of attack Ωgf, the shorter will be the atomized jet, and vice versa. This dimensioning parameter means that the device can be adjusted to suit different burners or methods according to the desired flame length.

The injector according to the invention is a highly effective atomization tool. It allows atomization performance to be achieved that is at least equivalent to the best atomizers of the prior art notably in terms of low atomization gas flow rates (ratio between the atomization gas flow rates and combustible liquid flow rates). In addition, the injector is highly reliable thanks to a simple design that allows for a one-piece construction exhibiting good resistance to high temperatures of the atomization unit. It allows very fine atomization of the combustible liquid and makes it possible to limit the increase in temperature of the mixture of atomization gas and combustible liquid that has been preatomized before being ejected into the hearth via the outlet opening.

Unlike multi-insert injectors, the injector according to the invention with a one-piece atomizer makes it possible to avoid leaks of combustible liquid and thus avoid impaired atomization and blockage of the atomizer through the formation of coke.

Because the injector and the burner according to the invention have a particularly low risk of blockage, this injector and this burner are particularly suited to being used for atomizing a combustible liquid in a combustion zone the atmosphere of which is highly laden with condensable substance(s) and/or pulverulent solid substance(s).

The injector according to the invention makes it possible to obtain an atomized jet made up of very fine droplets for low relative flow rates of atomization gas (low atomization gas (air)/combustible liquid (fuel) mass ratio) right from the outlet of the injector.

Specifically, this improved internal atomization method produces a dispersed mixture of liquid in the atomization gas right from its outlet without the formation of any true core of liquid.

The droplet size distributions obtained with this device result from a particularly fine atomization since for mass ratios of atomization gas flow rate to combustible liquid flow rate of 5 to 15% the SMD values range from 80 μm to under 60 μm when the atomization gas is air and the combustible liquid is heavy fuel No. 2 at 110° C.

The atomized jet formed is also very homogeneous because the droplet sizes measured are similar at the center and at the periphery of the atomized jet spray. 

1-15. (canceled)
 16. An injector for injecting an atomized jet spray of a combustible liquid through an outlet opening into a combustion zone situated downstream of the outlet opening of the injector, said injector comprising an internal assisted atomization unit that comprises a downstream injection face comprising said outlet opening, a combustible-liquid passage with an open downstream end, and two to six atomization gas ducts, wherein: said passage has a longitudinal axis of symmetry defining a direction Df of flow of the combustible liquid and a substantially circular variable cross section; said passage passing through said atomization unit and comprising a narrow part having a diameter φf, and a preatomization chamber of diameter greater than φf downstream of the narrow part; said preatomization chamber having an inlet opening and ending at said outlet opening which is situated opposite said inlet opening, a length Lc in said direction Df between said inlet opening and said outlet opening, and a mean diameter φc; said narrow part opening into said preatomization chamber via said inlet opening; said passage ending at its downstream end in said outlet opening of said injector; each of said ducts comprising a terminal section having a diameter φg, where φg<φf, each terminal section defining an associated direction of flow of the atomization gas and opening into said narrow part of said passage near said inlet opening of said preatomization chamber so that each of said associated directions of flow forms an angle Ωgf of between 30° and 90° with the direction of flow Df; said terminal sections open into said narrow part at a tangent to said narrow part so that the atomization gas impinges on the combustible liquid and imparts a helical movement to the combustible liquid; and said length Lc of said preatomization chamber is less than or equal to a mean diameter φc of said preatomization chamber.
 17. The injector of claim 16, wherein said atomization unit is in one piece.
 18. The injector of claim 16, wherein 0.2×φc<Lc≦φc, preferably 0.2×φc<Lc≦0.5×φc.
 19. The injector of claim 16, wherein 0.2×φc<Lc≦0.5×φc.
 20. The injector of claim 16, wherein said preatomization chamber comprises at least one substantially cylindrical portion.
 21. The injector of claim 16, wherein each of said associated directions of flow forms an angle Ωgf of between 35° and 85° with the direction of flow Df, preferably of between 40° and 80°.
 22. The injector of claim 16, wherein each of said associated directions of flow forms an angle Ωgf of between 40° and 80° with the direction of flow Df.
 23. The injector of claim 16, wherein 1.0<φc/φf<3.0.
 24. The injector of claim 16, wherein 0.1<φg/φf<1.0.
 25. The injector of claim 16, wherein 1.1<φc/φf<2.0.
 26. The injector of claim 16, wherein 0.2<φg/φf<0.8.
 27. A burner for burning a combustible liquid, comprising the injector of claim
 16. 28. A furnace for burning a combustible liquid comprising a hearth equipped with at least one injector according to claim 16 and a combustion zone downstream of the outlet opening of said injector.
 29. A furnace for burning a combustible liquid comprising a hearth equipped with at least one burner according to claim
 27. 30. A method for assisted internal atomization of a combustible liquid using the injector of claim 16, said method comprising the step of supplying the passage is supplied with combustible liquid and the ducts are supplied with pressurized atomization gas, so that: the combustible liquid has a flow velocity Vf in the narrow part of the passage, the atomization gas has flow velocities Vg in the terminal sections of the ducts, with Vg>Vf, and the atomization gas impinges on the combustible liquid and imparts a helical movement to the combustible liquid, wherein the atomized combustible liquid is injected into a combustion zone through the outlet opening of the injector.
 31. The method of claim 30, wherein the ducts are supplied with pressurized atomization gas in such a way that the flow velocities Vg of the atomization gas in the terminal sections of the ducts are greater than 80 m/s.
 32. The method of claim 30, wherein the ducts are supplied with pressurized atomization gas in such a way that the flow velocities Vg of the atomization gas in the terminal sections of the ducts are greater than 80 m/s and less than 600 m/s.
 33. The method of claim 30, wherein the passage is supplied with combustible liquid and the ducts are supplied with pressurized atomization gas so as to obtain an atomized jet spray of combustible liquid in the gas leaving the chamber with an ejection velocity comprised between 1 and 400 m/s, preferably between 100 and 350 m/s.
 34. The method of claim 30, wherein the passage is supplied with combustible liquid and the ducts are supplied with pressurized atomization gas so as to obtain an atomized jet spray of combustible liquid in the gas leaving the chamber with an ejection velocity comprised between 100 and 350 m/s.
 35. The method of claim 30, wherein the ducts are supplied with the pressurized atomization gas in such a way that the atomization gas is at a pressure of between 1 and 10 bar in the terminal sections of the ducts.
 36. A method for burning a combustible liquid in a hearth, comprising the steps of: supplying the passage is supplied with combustible liquid and the ducts are supplied with pressurized atomization gas, so that: the combustible liquid has a flow velocity Vf in the narrow part of the passage, the atomization gas has flow velocities Vg in the terminal sections of the ducts, with Vg>Vf, and the atomization gas impinges on the combustible liquid and imparts a helical movement to the combustible liquid, wherein the atomized combustible liquid is injected into a combustion zone through the outlet opening of the injector; and combusting the combustible liquid in the combustion zone with an oxidant in this combustion zone, the combustion zone being situated inside a hearth. 